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-rw-r--r--kernel/rcu/update.c366
1 files changed, 2 insertions, 364 deletions
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 74a698aa9027..c5799349ff31 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -514,370 +514,6 @@ int rcu_cpu_stall_suppress_at_boot __read_mostly; // !0 = suppress boot stalls.
EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress_at_boot);
module_param(rcu_cpu_stall_suppress_at_boot, int, 0444);
-#ifdef CONFIG_TASKS_RCU
-
-/*
- * Simple variant of RCU whose quiescent states are voluntary context
- * switch, cond_resched_rcu_qs(), user-space execution, and idle.
- * As such, grace periods can take one good long time. There are no
- * read-side primitives similar to rcu_read_lock() and rcu_read_unlock()
- * because this implementation is intended to get the system into a safe
- * state for some of the manipulations involved in tracing and the like.
- * Finally, this implementation does not support high call_rcu_tasks()
- * rates from multiple CPUs. If this is required, per-CPU callback lists
- * will be needed.
- */
-
-/* Global list of callbacks and associated lock. */
-static struct rcu_head *rcu_tasks_cbs_head;
-static struct rcu_head **rcu_tasks_cbs_tail = &rcu_tasks_cbs_head;
-static DECLARE_WAIT_QUEUE_HEAD(rcu_tasks_cbs_wq);
-static DEFINE_RAW_SPINLOCK(rcu_tasks_cbs_lock);
-
-/* Track exiting tasks in order to allow them to be waited for. */
-DEFINE_STATIC_SRCU(tasks_rcu_exit_srcu);
-
-/* Control stall timeouts. Disable with <= 0, otherwise jiffies till stall. */
-#define RCU_TASK_STALL_TIMEOUT (HZ * 60 * 10)
-static int rcu_task_stall_timeout __read_mostly = RCU_TASK_STALL_TIMEOUT;
-module_param(rcu_task_stall_timeout, int, 0644);
-
-static struct task_struct *rcu_tasks_kthread_ptr;
-
-/**
- * call_rcu_tasks() - Queue an RCU for invocation task-based grace period
- * @rhp: structure to be used for queueing the RCU updates.
- * @func: actual callback function to be invoked after the grace period
- *
- * The callback function will be invoked some time after a full grace
- * period elapses, in other words after all currently executing RCU
- * read-side critical sections have completed. call_rcu_tasks() assumes
- * that the read-side critical sections end at a voluntary context
- * switch (not a preemption!), cond_resched_rcu_qs(), entry into idle,
- * or transition to usermode execution. As such, there are no read-side
- * primitives analogous to rcu_read_lock() and rcu_read_unlock() because
- * this primitive is intended to determine that all tasks have passed
- * through a safe state, not so much for data-strcuture synchronization.
- *
- * See the description of call_rcu() for more detailed information on
- * memory ordering guarantees.
- */
-void call_rcu_tasks(struct rcu_head *rhp, rcu_callback_t func)
-{
- unsigned long flags;
- bool needwake;
-
- rhp->next = NULL;
- rhp->func = func;
- raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags);
- needwake = !rcu_tasks_cbs_head;
- WRITE_ONCE(*rcu_tasks_cbs_tail, rhp);
- rcu_tasks_cbs_tail = &rhp->next;
- raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags);
- /* We can't create the thread unless interrupts are enabled. */
- if (needwake && READ_ONCE(rcu_tasks_kthread_ptr))
- wake_up(&rcu_tasks_cbs_wq);
-}
-EXPORT_SYMBOL_GPL(call_rcu_tasks);
-
-/**
- * synchronize_rcu_tasks - wait until an rcu-tasks grace period has elapsed.
- *
- * Control will return to the caller some time after a full rcu-tasks
- * grace period has elapsed, in other words after all currently
- * executing rcu-tasks read-side critical sections have elapsed. These
- * read-side critical sections are delimited by calls to schedule(),
- * cond_resched_tasks_rcu_qs(), idle execution, userspace execution, calls
- * to synchronize_rcu_tasks(), and (in theory, anyway) cond_resched().
- *
- * This is a very specialized primitive, intended only for a few uses in
- * tracing and other situations requiring manipulation of function
- * preambles and profiling hooks. The synchronize_rcu_tasks() function
- * is not (yet) intended for heavy use from multiple CPUs.
- *
- * Note that this guarantee implies further memory-ordering guarantees.
- * On systems with more than one CPU, when synchronize_rcu_tasks() returns,
- * each CPU is guaranteed to have executed a full memory barrier since the
- * end of its last RCU-tasks read-side critical section whose beginning
- * preceded the call to synchronize_rcu_tasks(). In addition, each CPU
- * having an RCU-tasks read-side critical section that extends beyond
- * the return from synchronize_rcu_tasks() is guaranteed to have executed
- * a full memory barrier after the beginning of synchronize_rcu_tasks()
- * and before the beginning of that RCU-tasks read-side critical section.
- * Note that these guarantees include CPUs that are offline, idle, or
- * executing in user mode, as well as CPUs that are executing in the kernel.
- *
- * Furthermore, if CPU A invoked synchronize_rcu_tasks(), which returned
- * to its caller on CPU B, then both CPU A and CPU B are guaranteed
- * to have executed a full memory barrier during the execution of
- * synchronize_rcu_tasks() -- even if CPU A and CPU B are the same CPU
- * (but again only if the system has more than one CPU).
- */
-void synchronize_rcu_tasks(void)
-{
- /* Complain if the scheduler has not started. */
- RCU_LOCKDEP_WARN(rcu_scheduler_active == RCU_SCHEDULER_INACTIVE,
- "synchronize_rcu_tasks called too soon");
-
- /* Wait for the grace period. */
- wait_rcu_gp(call_rcu_tasks);
-}
-EXPORT_SYMBOL_GPL(synchronize_rcu_tasks);
-
-/**
- * rcu_barrier_tasks - Wait for in-flight call_rcu_tasks() callbacks.
- *
- * Although the current implementation is guaranteed to wait, it is not
- * obligated to, for example, if there are no pending callbacks.
- */
-void rcu_barrier_tasks(void)
-{
- /* There is only one callback queue, so this is easy. ;-) */
- synchronize_rcu_tasks();
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_tasks);
-
-/* See if tasks are still holding out, complain if so. */
-static void check_holdout_task(struct task_struct *t,
- bool needreport, bool *firstreport)
-{
- int cpu;
-
- if (!READ_ONCE(t->rcu_tasks_holdout) ||
- t->rcu_tasks_nvcsw != READ_ONCE(t->nvcsw) ||
- !READ_ONCE(t->on_rq) ||
- (IS_ENABLED(CONFIG_NO_HZ_FULL) &&
- !is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) {
- WRITE_ONCE(t->rcu_tasks_holdout, false);
- list_del_init(&t->rcu_tasks_holdout_list);
- put_task_struct(t);
- return;
- }
- rcu_request_urgent_qs_task(t);
- if (!needreport)
- return;
- if (*firstreport) {
- pr_err("INFO: rcu_tasks detected stalls on tasks:\n");
- *firstreport = false;
- }
- cpu = task_cpu(t);
- pr_alert("%p: %c%c nvcsw: %lu/%lu holdout: %d idle_cpu: %d/%d\n",
- t, ".I"[is_idle_task(t)],
- "N."[cpu < 0 || !tick_nohz_full_cpu(cpu)],
- t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout,
- t->rcu_tasks_idle_cpu, cpu);
- sched_show_task(t);
-}
-
-/* RCU-tasks kthread that detects grace periods and invokes callbacks. */
-static int __noreturn rcu_tasks_kthread(void *arg)
-{
- unsigned long flags;
- struct task_struct *g, *t;
- unsigned long lastreport;
- struct rcu_head *list;
- struct rcu_head *next;
- LIST_HEAD(rcu_tasks_holdouts);
- int fract;
-
- /* Run on housekeeping CPUs by default. Sysadm can move if desired. */
- housekeeping_affine(current, HK_FLAG_RCU);
-
- /*
- * Each pass through the following loop makes one check for
- * newly arrived callbacks, and, if there are some, waits for
- * one RCU-tasks grace period and then invokes the callbacks.
- * This loop is terminated by the system going down. ;-)
- */
- for (;;) {
-
- /* Pick up any new callbacks. */
- raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags);
- list = rcu_tasks_cbs_head;
- rcu_tasks_cbs_head = NULL;
- rcu_tasks_cbs_tail = &rcu_tasks_cbs_head;
- raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags);
-
- /* If there were none, wait a bit and start over. */
- if (!list) {
- wait_event_interruptible(rcu_tasks_cbs_wq,
- READ_ONCE(rcu_tasks_cbs_head));
- if (!rcu_tasks_cbs_head) {
- WARN_ON(signal_pending(current));
- schedule_timeout_interruptible(HZ/10);
- }
- continue;
- }
-
- /*
- * Wait for all pre-existing t->on_rq and t->nvcsw
- * transitions to complete. Invoking synchronize_rcu()
- * suffices because all these transitions occur with
- * interrupts disabled. Without this synchronize_rcu(),
- * a read-side critical section that started before the
- * grace period might be incorrectly seen as having started
- * after the grace period.
- *
- * This synchronize_rcu() also dispenses with the
- * need for a memory barrier on the first store to
- * ->rcu_tasks_holdout, as it forces the store to happen
- * after the beginning of the grace period.
- */
- synchronize_rcu();
-
- /*
- * There were callbacks, so we need to wait for an
- * RCU-tasks grace period. Start off by scanning
- * the task list for tasks that are not already
- * voluntarily blocked. Mark these tasks and make
- * a list of them in rcu_tasks_holdouts.
- */
- rcu_read_lock();
- for_each_process_thread(g, t) {
- if (t != current && READ_ONCE(t->on_rq) &&
- !is_idle_task(t)) {
- get_task_struct(t);
- t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw);
- WRITE_ONCE(t->rcu_tasks_holdout, true);
- list_add(&t->rcu_tasks_holdout_list,
- &rcu_tasks_holdouts);
- }
- }
- rcu_read_unlock();
-
- /*
- * Wait for tasks that are in the process of exiting.
- * This does only part of the job, ensuring that all
- * tasks that were previously exiting reach the point
- * where they have disabled preemption, allowing the
- * later synchronize_rcu() to finish the job.
- */
- synchronize_srcu(&tasks_rcu_exit_srcu);
-
- /*
- * Each pass through the following loop scans the list
- * of holdout tasks, removing any that are no longer
- * holdouts. When the list is empty, we are done.
- */
- lastreport = jiffies;
-
- /* Start off with HZ/10 wait and slowly back off to 1 HZ wait*/
- fract = 10;
-
- for (;;) {
- bool firstreport;
- bool needreport;
- int rtst;
- struct task_struct *t1;
-
- if (list_empty(&rcu_tasks_holdouts))
- break;
-
- /* Slowly back off waiting for holdouts */
- schedule_timeout_interruptible(HZ/fract);
-
- if (fract > 1)
- fract--;
-
- rtst = READ_ONCE(rcu_task_stall_timeout);
- needreport = rtst > 0 &&
- time_after(jiffies, lastreport + rtst);
- if (needreport)
- lastreport = jiffies;
- firstreport = true;
- WARN_ON(signal_pending(current));
- list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
- rcu_tasks_holdout_list) {
- check_holdout_task(t, needreport, &firstreport);
- cond_resched();
- }
- }
-
- /*
- * Because ->on_rq and ->nvcsw are not guaranteed
- * to have a full memory barriers prior to them in the
- * schedule() path, memory reordering on other CPUs could
- * cause their RCU-tasks read-side critical sections to
- * extend past the end of the grace period. However,
- * because these ->nvcsw updates are carried out with
- * interrupts disabled, we can use synchronize_rcu()
- * to force the needed ordering on all such CPUs.
- *
- * This synchronize_rcu() also confines all
- * ->rcu_tasks_holdout accesses to be within the grace
- * period, avoiding the need for memory barriers for
- * ->rcu_tasks_holdout accesses.
- *
- * In addition, this synchronize_rcu() waits for exiting
- * tasks to complete their final preempt_disable() region
- * of execution, cleaning up after the synchronize_srcu()
- * above.
- */
- synchronize_rcu();
-
- /* Invoke the callbacks. */
- while (list) {
- next = list->next;
- local_bh_disable();
- list->func(list);
- local_bh_enable();
- list = next;
- cond_resched();
- }
- /* Paranoid sleep to keep this from entering a tight loop */
- schedule_timeout_uninterruptible(HZ/10);
- }
-}
-
-/* Spawn rcu_tasks_kthread() at core_initcall() time. */
-static int __init rcu_spawn_tasks_kthread(void)
-{
- struct task_struct *t;
-
- t = kthread_run(rcu_tasks_kthread, NULL, "rcu_tasks_kthread");
- if (WARN_ONCE(IS_ERR(t), "%s: Could not start Tasks-RCU grace-period kthread, OOM is now expected behavior\n", __func__))
- return 0;
- smp_mb(); /* Ensure others see full kthread. */
- WRITE_ONCE(rcu_tasks_kthread_ptr, t);
- return 0;
-}
-core_initcall(rcu_spawn_tasks_kthread);
-
-/* Do the srcu_read_lock() for the above synchronize_srcu(). */
-void exit_tasks_rcu_start(void) __acquires(&tasks_rcu_exit_srcu)
-{
- preempt_disable();
- current->rcu_tasks_idx = __srcu_read_lock(&tasks_rcu_exit_srcu);
- preempt_enable();
-}
-
-/* Do the srcu_read_unlock() for the above synchronize_srcu(). */
-void exit_tasks_rcu_finish(void) __releases(&tasks_rcu_exit_srcu)
-{
- preempt_disable();
- __srcu_read_unlock(&tasks_rcu_exit_srcu, current->rcu_tasks_idx);
- preempt_enable();
-}
-
-#endif /* #ifdef CONFIG_TASKS_RCU */
-
-#ifndef CONFIG_TINY_RCU
-
-/*
- * Print any non-default Tasks RCU settings.
- */
-static void __init rcu_tasks_bootup_oddness(void)
-{
-#ifdef CONFIG_TASKS_RCU
- if (rcu_task_stall_timeout != RCU_TASK_STALL_TIMEOUT)
- pr_info("\tTasks-RCU CPU stall warnings timeout set to %d (rcu_task_stall_timeout).\n", rcu_task_stall_timeout);
- else
- pr_info("\tTasks RCU enabled.\n");
-#endif /* #ifdef CONFIG_TASKS_RCU */
-}
-
-#endif /* #ifndef CONFIG_TINY_RCU */
-
#ifdef CONFIG_PROVE_RCU
/*
@@ -948,6 +584,8 @@ late_initcall(rcu_verify_early_boot_tests);
void rcu_early_boot_tests(void) {}
#endif /* CONFIG_PROVE_RCU */
+#include "tasks.h"
+
#ifndef CONFIG_TINY_RCU
/*